Although not exactly your request as not in PDF, if the objective is purely to keep an offline copy of webpages for later review, saving it as webpage would do just that.
The big caveat is that it will create a .html file and a folder with all the media content on the page rather than a single document.
In Chrome and Firefox, you can save a page doing a right click on it and choosing Save as... In Internet Explorer, you can save it under File -> Save as (pressing the Alt key for the menus to appear).